[There's not a lot in J's life to make him contemplate his own mortality. There's the occasional near miss with a car, sure, and the far less occasional alien invasion, but this...]

[Well, this is on a whole other level. Nobody has ever literally changed their tune on him before, but that's what Sans has just managed to do, tune abruptly surging into something J wasn't even aware Sans had in him, something all power and rage, made all the more terrifying by the fact that it's still warping around brainwashing damage.]

[The flickering eye doesn't help either. He's seen enough horror movies to know that crazy eyes are a good indicator that there's a bad moon on the rise.]

[He messed this up, and if there's anything behind the wizard time scientist claims, he could very well die here. It's a sobering thought.]

[He doesn't flinch; he doesn't turn away; he's not running. Instead, he very calmly and deliberately removes his sunglasses, folds them, and slides them in his breast pocket. No sudden movements; no making it worse (or at least, he's trying not to make it worse).]

Honestly, I dunno how much I can tell you. It doesn't sound like you remember the last time we talked, but this time around I don't have a guarantee.